need new frame.
4BT is 50# heavier than stock 216 boat anchor. #775 or so.
6BT in running config is 1200#
4bt fits.
6bt means useing a GMC radiator, fan in front of radiator
or cutting doghouse into firewall.
google 6BT dimensions and you will find images with dimensions.
~25" 4bt
~35" 6bt
doghouse in your truck to fins on GMC radiator(farther from firewall than chevy rad) is about 36"
I have both in my yard.
drove 4bt in 8,000 firto van with chevy auto.
like it.
google 4BTswaps.com
free up your nights and just read all over the forum before oyu post and ask questions there-LOTS of info.
BTW-that MII wont be heavy enough for a 6BT.
period.
it MIGHT sustain a 4BT if you purchase adjustable coilovers that have teh correct spring rate.
personally-I would NOT use MII under either diesel.
not sturdy enough components.
maybe a narrowed 73-87 front truck suspension, maybe a camaro subframe.
maybe OEM front axle with coilover shocks.
